Quantum dot materials in general are made of semiconductor materials. Some semiconductor-based quantum material is made with cadmium and mercury sulfides and selenides, although possessing strong fluorescent emission properties, are high in toxicity because of the use of heavy metals in their production. Another downside to producing these kinds of quantum dots is their cost, due to the fact that the precursors used to make them can be expensive.
Carbon quantum dots (“CQD”) are attracting interest due to their high fluorescent quantum yield and low cytotoxicity. Areas of interest for use of carbon quantum dot nano-materials include chemical sensing, bio-sensing, bio-imaging, chemical sensing, nano-medicine, and photo-catalysis.
Although carbon quantum dots have been prepared in a variety of ways, most are top down synthesis that produce significant amounts of waste and require oxidative processing. In addition, current bottom up approaches have limited production capacity. Conventional means for producing CQD are electrochemical synthesis, laser ablation, arc discharge, microwave/ultrasonic synthesis and hydrothermal treatment. These methods of CQD production tend to be costly and yield a miniscule amount of product.
Magnesium metal is known to burn in carbon dioxide to produce carbon and magnesium oxide. It has been reported that few layer graphene forms from magnesium ribbon burned in a CO2 atmosphere; however, this reaction is uncontrollable and reaches quite high temperatures.
It is also known the CO2 is a by-product of various industrial activities such as ethanol production, distilleries, ammonia production or hydrogen reforming, not to mention the burning of fossil fuels. To that end, it is widely believed that human related CO2 emissions contribute to greenhouse effects in the atmosphere. Accordingly a need exists for scalable methods for producing carbon quantum dots that uses inexpensive waste gases, such as CO2, and does not require washing with cytotoxic reagents.